Chapter Three: In chapter one, we introduced the basic concepts of logic. But these depended on the somewhat vague notions of a "what is possible" and "what is not possible". So, for example, we said that an argument is valid if and only if it is not possible for its conclusion to be false while its premises are true. But what is possible is not always easily understood or even well defined. Still, now that we've introduced SL, we can say just what the concept of possibility is for the context of truth functional logic. This will allow us to precisely define all the basic logical concepts (like that of validity) first set out in chapter one. And it will provide a very straightforward test to see when these concepts correctly apply. For instance, we will provide a means to test whether or not an argument in SL is valid or not. Start with the introductory tutorials presented below, then print out the reference manual for this chapter (that way you'll have a concise statement of this chapter's details to refer to even when away from the computer.) Finally, and most importantly, carefully work your way through the chapter exercises. Tutorials for Chapter Three
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I Truth Tables (one row) 3.2ex
I Full Truth Tables (for simple sentences) 3.3ex
I Multiple Choice 3.4ex
I Multiple Choice 3.5ex
I Tables for Validity in SL Review Exercises:Crossword,Informal Proofs I, Informal Proofs II
